This invention pertains to apparatus for feeding fish in a fishpond or in a fish farming sea cage, and more particularly it pertains to an apparatus for screening and delivering moist fish feed pellets in an intermittent or pulsating mode.
Many fish growers believe that moist feed pellets are better than dry pellets to nourish a school of fish. The moist pellets sink quickly below the water surface where they are available to the younger and less vigorous fish. This feature is believed to be particularly advantageous when starting the rearing of a stock of young fish.
The handling of moist feed pellets, however, represents some difficulties. The moist material tends to form lumps that cannot be processed through a mechanical feeder. The moist material tends to stick to machine parts and to build up in the machine passages to clog the machine.
Another difficulty with the handling of moist fish feed is found in the separation of the fine particles from the moist pellets. It has been observed that a batch of fish feed can contain over 10% of fine particles and fragments of broken pellets. These fine particles and fragments, referred to as feed waste, are generally not eaten by the fish and sink through the mesh at the bottom of the sea cage. These particles accumulate over the bottom of the body of water under the sea cage and rot with fish excrement. Such accumulation of decaying material under the sea cage can promote the development of disease agents and cause other discomforts to the fish being reared at that location. Therefore, a fallow period is normally provided between growth periods to allow for natural cleansing of the cage site.
It will be appreciated that there are incentives for fish growers to reduce the pollution generated under a sea cage from the accumulation of waste feed, and by the same action to reduce the extent of the fallow periods. There are also economic incentives to separate and collect the feed waste at the feeder for later recycling into whole feed pellets. These incentives impose a heavy demand on the existing feeders. This demand is believed to be greater than the capacity available in the prior art.
Some of the prior art feeders produce a constant flow of feed material. Examples of these apparatus are described and illustrated in the following documents:
U.S. Pat. No. 4,832,538 issued on May 23, 1989 to Steve Bullerman et al.;
U.S. Pat. No. 4,984,536 issued on Jan. 15, 1991 to James W. Powell et al.;
U.S. Pat. No. 5,076,215 issued on Dec. 31, 1991 to Ning C. Yang, and
U.S. Pat. No. 5,337,698 issued on Aug. 16, 1994 to Ronald L. Widmyer.
Each of these apparatus uses a feed screw or a rotary valve to deliver a constant amount of feed material to the inlet of a venturi eductor, where the feed material is blown away in an air stream.
In another apparatus of the prior art, there is provided a system to recover feed waste falling at the bottom of a sea cage. The feed waste is then available for recycling. This system is described in the following document.
CA 2,145,338, a patent application published on Sep. 24, 1996.
In another type of apparatus, an endless belt conveyor with spaced-apart flights is used to feed the material out of a hopper and into a fish pen. A limited amount of material is carried out by each flight, and for this reason, these apparatus are capable of producing an intermittent flow of fish feed. Examples of equipment belonging of this group are described in the following documents:
U.S. Pat. No. 848,101 issued on Mar. 26, 1907 to H. S. Hale, and
U.S. Pat. No. 5,842,303 issued on Dec. 1, 1998 to George Abraham et al.
Because of their intermittent feed characteristics, the apparatus in this last group are believed to be efficient in delivery moist feed material without clogging. However, the designs of these apparatus do not offer any suggestion to recover the feed waste, or to deliver the feed pellets in an air stream. The apparatus from the first group using blowers do not offer any suggestion to prevent clogging when processing moist feed material, or to separate the feed waste from the whole feed pellets. Generally, the apparatus of the prior art have been used with limited success with moist fish feed, and therefore numerous fish growers still have recourse to hand feeding, despite the high labour cost of this practice.
As such, it may be appreciated that there continues to be a need for a new and improved apparatus to deliver moist fish feed in a reliable manner without clogging and with the ability to screen and recover the feed waste for recycling.
The present invention provides a feeder having screening abilities, an intermittent feed mode and an articulated air delivery system for dispensing moist feed pellets over a wide area of a fishpond or a sea cage with minimum or no clogging thereof.
In accordance with one feature of the present invention, there is provided a feeder for dispensing moist feed pellets to fish in a fish farming installation. The feeder comprises a feed storage hopper, a screen group to separate the feed material into edible-size pellets and feed waste, and a conveyor for conveying the feed material from the hopper to the screen group. The feed waste is collected in a receptacle for later recycling through a feed pellet extruder. The feeder also has an air delivery system for aspiring the edible-size pellets from the screen group and for delivering the pellets into an air stream directed toward a fish pen. Most importantly, the conveyor is a belt type conveyor with spaced-apart flights, providing this feeder with the ability to dispense discrete amounts of fish feed in an intermittent feed mode from the hopper, through the screen group and into the air delivery system.
One advantage of the intermittent feed mode is that it greatly reduces the sticking of moist feed material to the machine parts. It is therefore possible to screen the feed material to an extent which is unheard of with feeders of the prior art. During tests in an actual installation, a total of 10.9% of the feed material has been recovered as feed waste. This material was re-extruded and reuse. As one can imagine the recovery of this feed waste represents a substantial saving in feed cost to the fish grower.
In accordance with another feature of the present invention, the screen group comprises a primary and secondary screens, each having a different bar spacing, and a reciprocating mechanism affixed to the screens for vibrating the screens with different stroke lengths corresponding substantially to their bar spacings. This feature contributes to an efficient screening of the feed material without applying unnecessary stress on the feed pellets.
In yet another feature of the present invention, the air delivery system comprises a venturi eductor, a nozzle and an articulated support assembly for supporting and moving the venturi eductor and the nozzle from side to side and up and down. The air delivery system also comprises an accept belt conveyor having a discharge end. The venturi eductor comprises an inlet pipe having a mouth opening over the discharge end of the accept conveyor for aspiring feed pellets from the discharge end. The mouth opening has a D-like shape comprising a straight edge being contiguous with or near the surface of the conveyor. The articulated support assembly has a horizontal axis of articulation aligned with the straight edge and a vertical axis of articulation passing through a mid-point on the straight edge. This air delivery system is particularly appreciable for delivering feed pellets in many directions without losing the suction at the mouth opening of the inlet pipe.
In yet another aspect of the present invention, the articulated support assembly is movably mounted on the frame of the feeder and is adjustable in up and down directions to reduce or increase a gap between the straight edge of the mouth opening and the conveyor belt.
Other advantages and novel features of the present invention will become apparent from the following detailed description of the preferred embodiment.